Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$234.96	8.140%	$254.0857	$254.09	$254.10	$254.10
Purchase #2	$11.58	11.221%	$12.8794	$12.88	$12.90	$12.90
Purchase #3	$207.48	4.711%	$217.2544	$217.25	$217.25	$217.30
Purchase #4	$104.78	4.152%	$109.1305	$109.13	$109.15	$109.10
Purchase #5	$100.57	5.453%	$106.0541	$106.05	$106.05	$106.10
Purchase #6	$208.53	6.810%	$222.7309	$222.73	$222.75	$222.70
Purchase #7	$27.56	6.741%	$29.4178	$29.42	$29.40	$29.40
7 purchase totals =	$895.46		$951.5528	$951.55	$951.60	$951.60